Abstract: A retaining device has a multi-layer protective cladding for protecting the bearing and containment structure of a spreading chamber for the controlled spread and cooling of a melt from a nuclear reactor pressure vessel. The spreading chamber is configured under the spreading concept, i.e. the melt spreads and cools therein. The protective cladding has at least two layers: an outer sacrificial layer acts as a thermal shock barrier and melting substance; a protective and insulating layer, disposed inside the sacrificial layer and protecting the underlying bearing and containment structure, acts as thermal protection layer and retaining layer for the hot melt. The protective and insulating layer includes a first partial layer of fireproof concrete adjacent the bearing and containment structure, and a second partial layer of temperature-resistant ceramic blocks, in particular ZrO2 adjacent the sacrificial layer.

Abstract: A method is provided for performing nondestructive examination of a metal specimen using neutron activated positron annihilation wherein the positron emitter source is formed within the metal specimen. The method permits in situ nondestructive examination and has the advantage of being capable of performing bulk analysis to determine embrittlement, fatigue and dislocation within a metal specimen.

Abstract: A radioisotope production target and a method for fabricating a radioisotope production target is provided, wherein the target comprises an inner cylinder, a foil of fissionable material circumferentially contacting the outer surface of the inner cylinder, and an outer hollow cylinder adapted to receive the substantially foil-covered inner cylinder and compress tightly against the foil to provide good mechanical contact therewith.

Abstract: A technique for reducing the shadow corrosion effect in zirconium-based alloys caused by .beta.-particles emitted by adjacent components containing one or more elements that emit .beta.-particle flux when activated by neutron capture. The technique entails providing a coating capable of absorbing .beta.-particles, so as to mitigate the adverse effect of .beta.-particle bombardment of a zirconium-based alloy. Preferred coating materials include beryllia, beryllium, tin, zinc, chromium and cadmium. The coatings can be applied to various nuclear reactor structural alloys, such as stainless steel and nickel, platinum, copper, hafnium and yttrium-based alloys containing 0.2 weight percent manganese or more.

Abstract: A method and apparatus for mitigating oscillatory pressure disturbances that result from venting steam from a nuclear reactor into a pressure suppression pool through a plurality of spargers is disclosed. The individual spargers are connected in series so that a time delay exists between first venting of noncondensable gas and steam from successive spargers. This time delay can be adjusted so that the pressure disturbances from successive spargers are out of phase, partially or wholly canceling one another. This cancellation of oscillatory pressure disturbances minimizes dynamic loads on the walls of the suppression pool and on structures submerged in the suppression pool.

Abstract: A pyrolytic carbon coated nuclear fuel particle and method of making it. The fuel particle has a core composed of a refractory compound of an actinide metal. The pyrolytic carbon coating surrounds the core so as to provide a void volume therebetween. The coating has an initial density of no greater than 1.45 grams/cm.sup.3 and an anisotropy factor than 3.0 and a final density upon heat treatment above about 2000.degree. C. of greater than 1.7 grams/cm.sup.3 and an anisotropy factor greater than 5.

Abstract: A safety grade protection system for monitoring parameters indicative of the status of a core of a nuclear reactor, and reducing the criticality of the nuclear reaction when the onset of unsafe conditions are detected. The invention directly detects, in real time, the power at a plurality of axial and radial locations within or about the core and provides a three-dimensional real-time core power output. The system processes those outputs together with a measure of core coolant inlet temperature, pressure and flow rate to calculate, in real time, the fuel centerline temperature, the heat transfer condition at the fuel elements' boundary and the rate of power change within the core.

Abstract: Iodine-125 is produced by neutron irradiation of .sup.124 Xe gas to form .sup.125 Xe and permitting decay of .sup.125 Xe to form .sup.125 I. Irradiation of the xenon-124 is effected in a first chamber within an enclosure and decay is effected in a second chamber within the enclosure and free from neutron flux. The apparatus is submersible in a nuclear reactor pool so as to absorb any radiation escaping the apparatus during the process. Xenon can be caused to move between the chambers remotely, underwater. The second chamber is removable from said enclosure and is transported to a suitable location to recover the .sup.125 I from its interior. Such recovery is effected by admitting an aqueous wash solution into the second chamber, whereupon it is heated, causing water from the wash solution to reflux and cleanse the interior surfaces of the second chamber, thus creating an aqueous solution of .sup.125 I, which then is caused to drain into a suitable container.

Abstract: The top nozzle (6) of the fuel assembly includes a transverse adaptor plate (6a) penetrated by openings (8) for fastening the guide tubes (4) and by openings (9) for water to pass through. The water passage openings (9a) in the adaptor plate (6a) of the top nozzle (6) which are arranged in a central part of the adaptor plate (6a) have a triangular shape with rounded corners and are distributed regularly around at least some of the openings (8) for fastening the guide tubes (4).

Abstract: A reactor core for a boiling water nuclear reactor includes a plurality of fuel assemblies (40) with a plurality of vertical fuel rods (10) and possibly occasional vertical water-filled rods or channels (32, 48, 49, 50, 51) which are surrounded by a fuel channel (1). Between the fuel assemblies (40) there are arranged water gaps (37a, 37b). At least one fuel assembly (40) has at least one outer, reduced corner portion (41) facing a gap (37a, 37bb), and the number of fuel rods (10) in each such fuel assembly (40) is reduced by a number corresponding to the number of reduced corner portions (41) therein.

Abstract: Radionuclides are produced according to the present invention at commercially significant yields and at specific activities which are suitable for use in radiodiagnostic agents such as PET imaging agents and radiotherapeutic agents and/or compositions. In the method and system of the present invention, a solid target having an isotopically enriched target layer electroplated on an inert substrate is positioned in a specially designed target holder and irradiated with a charged-particle beam. The beam is preferably generated using an accelerator such as a biomedical cyclotron at energies ranging from about 5 MeV to about 25 MeV. The target is preferably directly irradiated, without an intervening attenuating foil, and with the charged particle beam impinging an area which substantially matches the target area.

Abstract: In an arrangement of an initial core, the core is loaded with 572 high enrichment fuel assemblies H with 4.2 wt % average enrichment and 300 low enrichment fuel assemblies L with 1.5 wt % average enrichment. The average enrichment of the core is about 3.3 wt %. In this core, only the low enrichment fuel assemblies are loaded into the most outer position of the core and the high enrichment fuel assemblies are loaded into an area other than the most outer position. In this arrangement, the average enrichment of reload fuel assemblies is 3.7 wt %.

Abstract: A nuclear fuel pellet having concentric layers of nuclear fuel in which an outer layer has less fissionable nuclear fuel per unit volume and substantially the same amount of fertile material per unit volume as an inner core.

Abstract: The fuel assembly includes an arrangement for quickly fixing the guide thimble into an opening passing through the adaptor plate of a dismountable nozzle of the assembly. This arrangement includes at least two bearing stops inside the opening of the nozzle, a bearing sleeve integral with the end of the guide thimble and a locking ring which includes stops for bearing on bearing surfaces of the stops inside the opening of the nozzle and deformable elastic parts capable of being accommodated in cavities of the opening of the adaptor plate or of the bearing sleeve, in order to place the ring in a position in which the guide thimble is locked or unlocked. The sleeve includes a rim for bearing on a bearing surface of the adaptor plate at the periphery of the opening.

Abstract: The electromagnetic drive mechanism for the control rods of a nuclear reactor has a stationary gripper and coil, a movable gripper and coil, and a lifting armature and coil for moving the movable gripper to advance or retract the control rods in steps. A coil current driver responsive to a controller provides currents to the coils individually and in combinations. During the operations, coil current signals are sensed, sampled, digitized and processed to generate coil current data such as amplitude as a function of time. The measured coil current data is compared to nominal current data as well as historical current data, and the historical data is updated or appended to include the measured data. The comparison includes a check for correct timing relationships, such as the timing of the current notch occurring due to increased inductance upon pull-in of a gripper.

Abstract: A nuclear fuel bundle has full-length and part-length fuel rods, the latter defining vent volumes interspersed among the full-length fuel rods. The vent volumes afford critical power enhancement by efficiently transferring liquid to adjacent full-length fuel rods. Except for full-length fuel rods adjacent unheated surfaces, for example, the channel and water rods, each fuel rod lies face adjacent a steam vent volume and full-length fuel rods diagonally adjacent a steam vent volume lie face adjacent at least one other steam vent volume whereby, except for full-length fuel rods adjacent non-heat generating surfaces, enhanced critical power performance is applicable to all full-length fuel rods notwithstanding diagonal location of full-length fuel rods relative to a steam vent volume.

Abstract: A nuclear fuel pellet having concentric layers of nuclear fuel in which an outer layer has less fissionable nuclear fuel per unit volume and substantially the same amount of fertile material per unit volume as an inner core.

Abstract: A beam of accelerated charged particles irradiates an arsenide target, such as gallium arsenide or aluminum arsenide, to produce radioisotopes of selenium and other radionuclides. The irradiated target is placed in a niobium, tantalum, or graphite vessel and inserted into a tube. Metallic reagents consisting of an alloy of iron, nickel, and chromium (stainless steel) or metallic aluminum are mixed with the target material. The target is then heated to 1000-1100.degree. C. The metallic reagents prevent arsenic sublimation, destroy the crystalline structure of arsenide target, and remove other impurities, such as zinc-65. The target is then heated a second time to about 1300.degree. C. causing the selenium-72 to sublime and be deposited on a cooler wall of the tube or on a catcher foil surface. The deposited selenium-72 is recovered from the tube or foil.

Abstract: The operator of a nuclear steam supply system manually selects a lineup of either one, two, or three main feedwater pumps for normal reactor operation to generate power. This selection sets or resets a status latch for each pump, representative of intended pump operation.

Abstract: A steam/water separating device for a nuclear fuel bundle is located in a vent volume above part-length rods and includes a helical swirl vane. In one form, the swirl device lies below a vent tube and a transition element for flowing liquid laterally outwardly into the interstices of the fuel rods and steam upwardly within the vent tube. In another form, the vane depends from a cylindrical barrel open at its lower end. An annular pick-off tube extends into the open upper end of the barrel and lies in communication through a transition element with a superposed steam vent tube. An annular outlet is defined between the barrel and pick-off tube and the transition element deflects coolant water flowing through the annular outlet in a lateral outward direction for flow into the interstices of and onto the full-length fuel rods. Steam flows upwardly in the barrel through the pick-off tube into the steam vent tube.